Search Results (142)

Metamaterials with tailored structural architectures enable negative thermal expansion through geometric mechanisms that counteract constituent-level positive expansion. This study evaluates the thermomechanical performance and structural limits of polymer and hybrid NTE lattices. We systematically classify the dominant kinematic mechanisms, including bimetallic bending, rotational squares, and re-entrant honeycombs, and quantify the inherent trade-offs between effective thermal contraction, structural stiffness, and mass efficiency. The analysis demonstrates that reliance on idealized linear–elastic and rigid-lever models leads to significant predictive discrepancies when evaluating the physical response of polymeric and hybrid prototypes. We establish that these deviations are fundamentally governed by localized stress singularities at multi-material interfaces and the profound thermoviscoelastic softening of polymers as they approach the glass transition temperature ($T_g$). We conclude that accurate prediction of the cyclic lifespan and dimensional stability of these systems requires a transition to coupled multiphysics frameworks. Specifically, integrating temperature-dependent cohesive zone modeling and time–temperature superposition principles is essential for capturing interfacial delamination and thermal ratcheting in high-performance polymeric NTE metamaterials. Full article

Temperature is a physical quantity that represents the degree of heat or cold of an object and has significant application value across various fields. Traditional contact temperature measurement technologies, such as thermocouples and infrared thermometers, suffer from limitations like poor environmental adaptability and low spatial resolution, which makes it difficult to meet the temperature measurement requirements for micro-/nano-devices and extreme environments. In recent years, non-contact optical temperature measurement technology based on the luminescence characteristics of rare earth ions has garnered widespread attention due to its high sensitivity, strong interference resistance, and good environmental adaptability. In addition to inorganic luminescent materials, lanthanide-based molecular and coordination-complex thermometers have also become an important branch of this field; however, this paper focuses on inorganic rare earth luminescence thermometry. This paper provides a systematic review of the mechanisms of temperature measurement using rare earth ion luminescence, including single-energy-level luminescence intensity measurement and luminescence intensity ratio measurement based on thermally coupled levels (TCLs) and non-thermally coupled levels (NTCLs). It analyzes the principles of various technologies, performance parameters (such as absolute sensitivity S_a, relative sensitivity S_r, and temperature resolution δT), and their application progress in fields such as biomedical imaging, high-temperature aerospace environments, and the integration of micro-/nano-devices. Special attention is paid to emerging research directions, including Stark sublevel engineering for enhanced sensitivity, negative thermal expansion (NTE) host design for anti-thermal quenching, multi-modal collaborative thermometry, and artificial intelligence (AI)-assisted material design and data processing. The article also discusses the challenges currently faced by the technology, such as high-temperature fluorescence quenching and signal interference, and looks forward to future development directions, including artificial intelligence-assisted material design and multi-modal cooperative temperature measurement, aiming to provide a reference for the research and application of rare earth luminescence temperature sensing technology. Full article

This study presents the development of an eco-friendly brick for mining, a sustainable composite material manufactured from gold mine tailings and used cooking oil (UCO) through a thermal oxypolymerization process. Unlike conventional stabilization methods, which often require additional materials beyond tailings or have a high carbon footprint in their production, this approach uses oxypolymerization to transform these two waste products into novel building materials. The use of various percentages of UCO at different heating temperatures was evaluated to identify the optimal mixture, determining that a 9% UCO content and a 9 h cycle are key conditions for inducing fatty acid crosslinking. This logical relationship between heat treatment and dosage allows the organic binder to consolidate the mineral matrix, giving the material a compressive strength of 19.12 MPa and a flexural strength of 8.24 MPa, exceeding the thresholds of the NTE INEN 297 standard. The low water absorption (2.86%) is attributed to the densification of the matrix and the hydrophobic nature of the polymerized oil, indicators of its structural durability. This work is the first to use Ecuadorian tailings as the sole mineral aggregate, validating a high-efficiency, low-impact product for sustainable construction under the principles of the circular economy. Full article

Corn tortillas are consumed daily in Mexico. Alkaline extrusion is an alternative process that generates nixtamalized tortillas and preserves more bioactive compounds. Chickpea germination-extrusion may enhance the bioactive compound content. The aim was to characterize the physicochemical and antioxidant/antidiabetic properties of functional tortillas of alkaline-extruded blue corn (TC) with germinated (TG) or germinated-extruded (TGE) desi-chickpea. Likewise, the effect of simulated gastrointestinal digestion (SGD) on the bioaccessibility of bioactive compounds (phenolics, soluble protein, peptides, anthocyanins, and isoflavones) was estimated. Antioxidant capacity/cellular activity was determined by ORAC (AoxC) and in the Caco-2 cell line (CAA), while antidiabetic potential by α-amylase inhibition. The supplementation with processed chickpeas (TG/TGE) increased protein, ash, and isoflavone content (p < 0.05) compared with TC. SGD (%) released (p < 0.05) bioactive compounds from tortillas, and their bioaccessibility was among 34–70%; noticeably low phenolic bioaccessibility in TG/TGE. The AoxC was higher in TG/TGE (p < 0.05) compared with TC; in contrast, CAA was higher in TC, and both increased after SGD. TG depicted the lowest amylase inhibition; after SGD, the IC₅₀ values were 62–72-fold lower in the digests than in the tortillas. These results suggest that functional tortillas with processed chickpeas enhance nutraceutical potential. Full article

The present study examined for the first time the effect of native yeasts on the fermentation of artisanal Spondias purpurea L., wine produced in Santa Elena, Ecuador. To achieve this goal, three inoculation strategies were compared: a mixed culture containing Saccharomyces cerevisiae and Candida spp. (CLX), commercial S. cerevisiae (CL), and a spontaneous fermentation without added inoculum (SL). Five yeast isolates were identified from the fermentations, four belonging to Candida spp. and one to Kloeckera spp., using microbiological and biochemical methods. The CLX treatment showed the greatest yeast proliferation on PDA plates (2.7 × 10⁶ CFU/mL) and yielded the highest levels of higher alcohols, while the CL treatment produced the highest ethanol (3.72% ABV) and glycerol content (0.46%). All treatments were free of total and fecal coliforms, and their pH values (2.49–2.56) satisfied the requirements of the current Ecuadorian standard for wine production NTE INEN 374. Residual glucose content was specifically quantified using an enzymatic colorimetric (GOD-POD) assay, confirming the dry character of the wines. Molecular analysis of the final preparation obtained from the variant corresponding to the spontaneous fermentation without inoculum (SL) confirmed the presence of Hanseniaspora spp. (Kloeckera spp.), Diutina rugosa (C. rugosa), C. zeylanoides and Pichia kudriavzevii, after the obtained PCR amplicons using ITS1 and ITS4 were subjected to a blast analysis. Sensory evaluation by panelists (n = 15) favored the CLX wine, particularly for aroma and flavor attributes. The final glucose content reached a low value of 0.28 g/L, indicative of an extremely dry wine, with almost no fermentable sugar. Due to the lack of information related to wines produced from Spondias purpurea L., this study could contribute to a better understanding of the biological behavior and biodiversity of the microorganisms present in this fermentation process. These findings will help to improve wine regionality production, supporting the potential application of native regional yeasts in Spondias purpurea L. wine biotechnology. Full article

This study presents a technical case study aimed at evaluating the emission performance and regulatory compliance of a low-level ethanol–gasoline blend (E5) produced from cocoa mucilage, applied in a spark-ignition vehicle applied in a spark-ignition vehicle without a catalytic converter, evaluated as a technical case study representative of aging fleet conditions. A controlled within-vehicle experimental design was employed to compare three fuels: Extra gasoline, Super gasoline, and an E5 blend (95% gasoline–5% bioethanol). Exhaust emissions carbon monoxide (CO), hydrocarbons (HC), carbon dioxide (CO₂), oxygen (O₂), and excess air ratio (λ) were quantified under standardized operating conditions (700 and 2500 rpm), following the Ecuadorian standard NTE INEN 2204:2017. Results demonstrate that the E5 blend improves combustion efficiency, reducing CO and HC emissions while increasing CO₂, indicating enhanced carbon oxidation. A systematic shift toward leaner combustion conditions (higher λ and O₂) was also observed, associated with the oxygenated nature of ethanol and improved air–fuel mixture homogeneity. However, regulatory assessment revealed only partial compliance, as all fuels met CO limits but exceeded thresholds for HC, λ, and O₂. Quantitatively, the E5 blend reduced CO emissions by approximately 10–15% compared to Extra gasoline and decreased HC emissions by approximately 15–25%, depending on the operating condition. Additionally, CO₂ emissions showed a slight increase, indicating improved combustion efficiency, while λ and O₂ values reflected a shift toward leaner combustion conditions. Overall, the findings highlight the dominant influence of vehicle mechanical condition on emission performance. Full article

The growing accumulation of microplastics in marine environments demands fast and accurate analytical methods for polymer identification. This study presents a new canonical spectral transformation (CST) strategy designed to extract the most relevant information of Raman spectra and enhance the performance of artificial intelligence (AI) models in the classification of microplastics. Using the Marine Plastic Database (MPDB) as the source of Raman spectra, five supervised models—k-Nearest Neighbor (KNN), Random Forest (RF), Extreme Gradient Boosting (XGBoost), Multilayer Perceptron (MLP), and a one-dimensional Convolutional Neural Network (CNN-1D)—were trained and evaluated under both typical (conventional methodology) and CST workflows using 500 noisy samples per category. The CST consists of representing a Raman spectra in a vector where only the magnitude peaks of the most relevant frequency bands of the spectra are retained and the remaining values are null. This CST minimizes the inclusion of non-target data reaching the AI models. All models achieved higher accuracy with CST, where CNN-1D achieved the most significant performance, increasing accuracy to 0.90. In addition, CNN-1D identified Polystyrene (PS) and Poly(methyl methacrylate) (PMMA) with a score of 100% and 99%, respectively. The results demonstrate that CST effectively enhances spectral feature extraction and can be generalized to other spectroscopic techniques, providing a scalable framework for AI-assisted microplastic identification in seawater samples. Full article

Chirostoma humboldtianum is an endemic atherinopsid from Mexico that has been of high socio-cultural and economic importance since pre-Hispanic times. It was the first ictic species from Mexico described for science, and it is considered the basal species that gave rise to a nominal group known as white fish or silversides. The aim of this research was to analyze semen quality in relation to breeding fish size and its effect on sperm cryopreservation during an annual cycle. Sexually mature males were collected from January to December 2023, in San Felix dam, Tiacaque, Mexico State, Mexico. The water temperature was measured, and the photoperiod was obtained from the Instituto Nacional de Geografía y Estadística (INEGI). Males were classified into two groups of total length (TL) after analyzing the variation in TL through a size histogram: (G1) 9–13 cm and (G2) longer than 13 cm. Semen volume (µL), sperm concentration (cells µL⁻¹), and motility percentage (%) were determined in all individuals of each group. Likewise, eight straws were cryopreserved per month per group, each one with 10 µL of semen from a mixture of three randomly selected individuals and cryopreserved at −196 °C for 72 h. The post-thawing motility percentage was subsequently verified. Males produce semen continuously all year round, with two periods of higher volume, March and June–August, defining two reproductive periods. The beginning of the first one coincides with the increase in water temperature, from 13 ± 2 to 18 °C. Males with a length more than 13 cm had a higher semen production compared to smaller males (17.33 ± 7.34 and 12.52 ± 4.41 µL, respectively, p < 0.05). The largest semen volumes were registered in March and from June to August in both groups. However, G2 males presented with a larger semen volume. Both groups had a marked decrease in a similar manner in April–May and September to January (p < 0.05). Sperm concentration was similar throughout the year in both groups (p > 0.05) (G1 = 1.35 ± 0.36 × 10⁶ µL⁻¹) (G2 = 1.31 ± 0.35 × 10⁶ µL⁻¹). In addition, fresh sperm motility was high in both groups (G1 = 96 ± 3%, G2 = 97 ± 4%) (p > 0.05). The highest sperm concentrations were observed in March to July, through to October for both groups (p > 0.05), while post-thaw sperm motility decreased by about 50% (G1 = 45 ± 4%) (G2 = 46 ± 6%) during the annual cycle (p > 0.05). The largest post-thaw motility was observed in March and from July to September in G1 and in March and from June to October in G2. Analysis of semen quality throughout the annual cycle reveals aspects of the reproductive biology of C. humboldtianum, including two reproductive peaks and continuous semen production. Full article

Tri-o-cresyl phosphate (TOCP) is widely used as a plasticizer, flame retardant, and lubricant additive, but has been reported to impair spermatogenesis. However, how TOCP affects spermatogenesis remains unclear. Therefore, the objective of this study is to investigate the underlying mechanism by which TOCP disrupts spermatogenesis. In order to achieve this, adult male mice were orally administered TOCP at doses of 0, 200, or 400 mg/kg for two weeks, and we found that TOCP exposure reduced the number of germ cells and decreased sperm density. Moreover, the numbers of PCNA-positive cells and phospho-histone H3 (Ser10)-positive cells in mouse testicular tissues were significantly decreased following TOCP treatment, indicating that germ cell proliferation may be impaired. In addition, TOCP did not affect the protein expression of neuropathy target esterase (NTE) in testicular tissues but markedly inhibited its enzymatic activity (by approximately 30% relative to the control level). In vitro experiments further demonstrate that TOCP suppressed cell proliferation and mitotic progression in mouse GC-1 spg cells and excessively activated endoplasmic reticulum (ER) stress. Treatment with 4-phenylbutyric acid (4-PBA), an ER stress inhibitor, partially reversed the TOCP-induced inhibition of cell proliferation and mitosis. Furthermore, TOCP inhibited NTE activity in GC-1 spg cells, and NTE knockdown produced a phenotype similar to that observed after TOCP exposure, characterized by suppressed cell proliferation and mitotic progression. Surprisingly, ER stress was not activated in GC-1 spg cells following NTE knockdown. Collectively, these findings suggest that TOCP may impair spermatogenesis by inhibiting the proliferation and mitotic progression of mouse germ cells, potentially through mechanisms involving excessive activation of ER stress or suppression of NTE activity. Full article

A substantial number of students with hearing impairments are enrolled in higher education, motivating the development of inclusive assistive technologies that reduce communication barriers. This study developed and evaluated a prototype electronic glove that translates Mexican Sign Language (LSM) signs into Spanish text using machine learning. Eight participants (four deaf and four hearing with LSM proficiency) completed four sessions involving 12 signs; three sessions (S1–S3) were used for model development and one session (T) was held out for evaluation. Models were trained on S1–S3 and tested on T using a session-level split without window mixing across sessions; therefore, results represent a speaker-dependent, inter-session pilot assessment rather than a speaker-independent generalization test. The glove integrates flex sensors and an inertial measurement unit IMU MPU6050 connected to an ESP32-C3 SuperMini microcontroller. These components were selected due to their low cost, availability, and ease of integration, making them suitable for the development of accessible wearable assistive technologies. Under this protocol, the system achieved a window-level overall test accuracy of 97.0% (95% CI computed at the window level: 96.00–97.00), with higher performance for the dynamic subset (98.0%) than for the static subset (95.0%), and an algorithmic decision delay of 1.2 s. Usability and acceptance were evaluated using the System Usability Scale (SUS) and a Technology Acceptance Model (TAM)-based questionnaire. The mean SUS score was 50.6 ± 1.8 (marginal usability), while participants reported positive perceptions across TAM constructs. Overall, findings demonstrate technical feasibility under controlled inter-session conditions and provide a foundation for iterative user-centered refinement, followed by strict speaker-independent validation and classroom deployment studies in future work. Full article

Microwave sintering enabled the efficient fabrication of bulk Mn₃Cu_0.5Ge_0.5N_0.9C_0.1 NTE materials in 3–5 h, versus 2 to 8 days for conventional methods. The microwave approach demonstrated high efficiency and energy savings. By adjusting temperature and dwell time, the NTE operating range can be shifted to lower temperatures. Under the optimized condition of 800 °C for 4 h, the resulting bulk material achieved an NTE coefficient of −20.56 × 10⁻⁶ K⁻¹ over a temperature interval ΔT of 88 K (from 159 K to 247 K), along with favorable densification and high hardness. The demonstrated processing efficiency, microstructural control, and tunable NTE properties establish a solid foundation for potential industrial scale-up. Full article

An attractive cryogenic near-zero thermal expansion (ZTE) behavior was achieved in the Mn₃Cu_0.5Ge_0.5N_0.78C_0.22 compound, spanning a broad temperature window of 120 K (5 K to 125 K) with an average coefficient of thermal expansion (CTE) of α = 0.68 × 10⁻⁶ K⁻¹. Furthermore, the effect of sintering temperature and holding time on thermal expansion and magnetic properties were investigated. Two distinct magnetic phase transitions are evident in the magnetization–temperature (M-T) curve of Mn₃Cu_0.5Ge_0.5N_0.78C_0.22, which precede the near-ZTE behavior. These two antiferromagnetic (AFM)-like ordering transitions are hypothesized to play a pivotal role in governing the ZTE behavior, as they induce two episodes of negative thermal expansion (NTE). The realization of ZTE behavior is thus attributed to the counterbalance of these two NTE contributions, which can be effectively tuned by varying the carbon content or optimizing the sintering process parameters. Collectively, these results demonstrate significant potential for the design of diverse cryogenic functional materials. Full article

Nighttime tourism has become a key driver of urban nighttime economic development. The nighttime tourism experiencescape (NTE)—comprising elements such as atmospheric lighting landscapes, culturally distinctive night markets, and diverse entertainment formats—creates an environment markedly distinct from daytime settings. This NTE significantly influences tourist experiences and contributes critically to the sustainable development of urban destinations. Grounded in the Stimulus–Organism–Response framework, this study investigates how the NTE shapes tourist loyalty. Empirical results indicate that the effect of the NTE on tourist loyalty is primarily mediated by place attachment, with place dependence demonstrating a stronger mediating effect than place identity. In the direct pathway, only the socio-symbolic dimension of the NTE exerts a significant positive impact on tourist loyalty. The study offers both theoretical and practical contributions: it reveals the mechanisms that influence tourist loyalty in nocturnal contexts and offers actionable insights into the sustainable management of nighttime tourism in urban destinations. Full article

In response to Ecuador’s need for sustainable and locally sourced transport fuels, this study evaluates the energetic and environmental performance of a biofuel (bioethanol-based) derived from the mucilage of the CCN51 cocoa variety, analyzed under controlled operating conditions in an internal combustion engine. Bioethanol obtained from this feedstock was blended with Ecuador’s commercial Extra gasoline to produce an E5 formulation, experimentally compared with Extra (85 RON) and Super (92 RON) fuels. Physicochemical analysis following NTE INEN 2102 revealed a research octane number of 85.8 and a lower heating value of 45.22 MJ/kg. Static tests performed on a Hyundai i10 engine (2021) at 700 and 2500 rpm showed that the E5 blend achieved higher energy and exergy efficiencies (21.17% and 64.12%, respectively) than Extra gasoline, approaching Super performance. Environmentally, the E5–CCN51 blend reduced carbon monoxide (CO) by ~10–15% and unburned hydrocarbons (HC) by ~5–8%, while maintaining λ ≈ 1. Variations in O₂ and CO₂ confirmed enhanced oxidation and more complete combustion. Overall, these findings demonstrate the technical feasibility and environmental relevance of CCN51 cocoa mucilage as a sustainable ethanol source, contributing to cleaner combustion, circular bioeconomy promotion, and energy resilience in tropical developing regions. Full article

This study validates an empirical model of attitudinal indicators to assess the inclusion of students with physical motor disabilities in higher education. Grounded in the tripartite model of attitude and framed within the social model of disability, the research employed the SACIE-R scale to measure emotional, cognitive, and behavioral predispositions among 384 faculty members from private universities in El Salvador, selected through stratified sampling. Exploratory factor analysis (EFA) identified three latent dimensions—concerns and general attitudes, inclusive feelings, and cognitive–affective tension—explaining 56.36% of the variance, with strong reliability (Cronbach’s α = 0.876). Chi-square tests revealed significant attitudinal differences by age, sex, training, and institutional affiliation. The resulting model translates latent predispositions into observable indicators of inclusive teaching competencies, providing a diagnostic and evaluative tool for higher education institutions. Beyond the Salvadoran context, the framework demonstrates potential scalability across Latin American systems with comparable socio-educational conditions. Importantly, the model contributes to the Sustainable Development Goals (SDG 4, SDG 10, and SDG 16) by supporting inclusive and equitable quality education, reducing structural inequalities, and informing governance policies grounded in human rights. Findings highlight persistent attitudinal barriers and limited faculty preparedness, underscoring the need for sustainable institutional strategies. This research advances the debate on educational sustainability by linking faculty attitudes to long-term policy development, capacity-building, and institutional accountability. Full article